Vibration minimization towing hitch

ABSTRACT

A vibration minimization towing hitch includes a shank attachable into the receiver tube the towing vehicle, and a separately formed head, such as for supporting a tow ball. The head is pivotable through a partial range of motion relative to the head, such as allowing the tow ball to pivot up to 7° downward or up to 3° upward. One or more compressible inserts are disposed in a pocket between the shank and the head, for resisting the limited pivotal motion of the head relative to the shank. A user performs a part of the assembly using two insertable pins or bolts, with insertion of the second pin compressing a compressible bumper which is separate from the insert(s).

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority from U.S. ProvisionalApplication No. 62/715,415 entitled VIBRATION MINIMIZATION TOWING HITCHfiled Aug. 7, 2018, incorporated herein by reference. The presentapplication also claims priority from U.S. Provisional Application No.62/805,443 entitled COMPRESSIBLE ANTI-RATTLE TOW BUMPERS filed Feb. 14,2019, incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention is directed to the field of towing, andparticularly to the structure to transmit towing force between a towingvehicle and a towed load. In this field, the issue of minimizingvibrations between the towed load and the towing vehicle, includingminimizing jerk while towing and minimizing noise, vibration andharshness, is well known. Many solutions to the issue include using aspring and/or dampening member as part of the structure transmitting towforces. Examples include U.S. Pat. Nos. 2,878,036, 4,773,668, 4,817,978,5,823,560, 5,975,553, 6,581,953, 6,834,879, 7,093,845, 9,505,281 and9,868,327, all incorporated by reference for their teachings of theproblem and materials used for the functioning of the variouscomponents.

Several of these prior art hitches allow relative movement between thehitch and the hitch receiver and attempt to then dampen or provide abiasing spring force on such movement. However, this generally leavesthe spring and/or dampening member exposed before or after installationinto the hitch receiver, requiring the user to correctly position andattach the spring and/or dampening member relative to the hitchreceiver. The hitch receiver on all vehicles is not exactly uniform, andthe positioning and attaching of the spring and/or dampening memberrelative to the hitch receiver may be inconsistent as performed by theend user, leading to inconsistent spring or dampening forces from oneinstallation to the next.

Several of these prior art hitches involve a sliding, linear movementcausing compression or extension of the spring and/or dampening member,in an amount substantially equal to the amount of give or movement inthe hitch. As a general statement, when involving such a length ofmovement, wear or deterioration of the spring and/or dampening member islikely to occur, leading to an unacceptable possibility of catastrophicfailure.

Several of these prior art hitches involve a torsion force on the springand/or dampening member. Like the long-length linear movement, thetorsional forces tend to rapidly wear or degrade the spring and/ordampening member leading to an unacceptably short hitch productlifespan. Separately, if the spring or dampening member is based oncompression of a polymer material, several of these prior art hitchesunacceptably concentrate that compression on a specific, vulnerable areaof the polymer material, leading to wear, degradation, and decrease inperformance over time.

In some prior art hitches, there is equipment which is regularlyassembled and disassembled, on multiple occasions, by the user, usingtwo bolts or pins for the assembly and disassembly. Examples include theequipment taught in U.S. Pat. Nos. 3,600,004, 3,731,950, 4,211,427,5,375,867, 5,647,603, 5,873,594, 6,722,682, 7,025,370, 8,328,222 and10,183,536, all incorporated by reference. To speed the process ofassembly or disassembly, the two bolts or pins are not threaded alongtheir entire length, but rather have a substantial length (in some casesthe entire length which is inserted into their hole) which has a smoothshaft. In general, in order for the user to be able to insert and removethe bolts or pins by axially sliding (rather than rotational, threadedadvancement), there must be clearance between the smooth shaft and themating hole. For instance, when using 20 mm diameter pins, a typicalnominal (as designed) clearance might be 1 mm. Because there is amanufacturing tolerance on both the pin and the pin hole, this willcommonly result in the actual clearance between the pin and the pin holein the 0.5-1.5 mm range.

In these various examples, the two bolts or pins are horizontallydisposed, withstanding the primary towing forces not in an axial tensionforce on the bolts or pins, but rather as one or more shear forceimposed between aligned holes acting on the shafts of the bolts or pins.The primary towing forces include not only the tow force in thedirection of travel of the towing vehicle, but also a vertical force oftongue weight. While the tow force changes direction frequently duringtowing as the towing vehicle accelerates and decelerates, the tongueweight stays much more consistent, such as pushing downward on a ball ofthe hitch and only very rarely (over very rough road or terrain) pullingupward on the ball of the hitch.

One detractor and common complaint for such equipment is that equipmentmakes excessive noise and rattles too much. The rattle is often worsewhen the equipment is unloaded, i.e., when not pulling a trailer orsimilar load. Many different types of anti-rattle structures have beenproposed for various hitch equipment, but better solutions are needed.

Moreover, as a general statement, these prior art towing hitches aregenerally complicated and relatively expensive to manufacture. Bettersolutions are needed.

BRIEF SUMMARY OF THE INVENTION

The present invention is a towing hitch to transmit a towing forcebetween a towing vehicle and a towed load. The towing hitch includes ashank attachable into the receiver tube the towing vehicle, and aseparately formed head, such as for supporting a tow ball. In oneaspect, the head is pivotable through a partial range of motion relativeto the head. One or more compressible inserts are disposed between theshank and the head, for resisting the limited pivotal motion of the headrelative to the shank. The insert is preferably protected within apocket between the shank and the head. In another aspect, a userperforms a part of the assembly using two insertable pins or bolts. Abumper formed of a compressible material is positioned so as to take upthe play between the pins and their holes, asserting a biasing forceafter the user inserts the first pin so the user can insert the secondpin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear perspective view of a preferred embodiment of avibration minimization ball mount towing hitch of the present invention,assembled with the tongue member secured in the lowest elevationalposition.

FIG. 2 is a side view (from the driver's side) of the towing hitch ofFIG. 1.

FIG. 3 is an opposing side view (from the passenger's side) of thetowing hitch of FIGS. 1 and 2.

FIG. 4 is a rear view of the towing hitch of FIGS. 1-3.

FIG. 5 is a front view of the towing hitch of FIGS. 1-4.

FIG. 6 is a top view of the towing hitch of FIGS. 1-5.

FIG. 7 is a bottom view of the towing hitch of FIGS. 1-6.

FIG. 8 is an exploded rear perspective view of the towing hitch of FIGS.1-7, illustrating the user assembling of the tongue assembly of thetowing hitch to the shank/head assembly.

FIG. 9 is an exploded rear perspective view of the shank/head assemblyof FIGS. 1-8, illustrating the manufacturer assembling of the shank/headassembly.

FIG. 10 is a side view of the shank of the towing hitch of FIGS. 1-7.

FIG. 11 is a horizontal cross-sectional view of the shank of FIG. 10,taken along lines 11-11.

FIG. 12 is a vertical cross-sectional view of the shank of FIG. 10,taken along lines 12-12 in FIG. 11, and further showing a side view ofthe compressible insert oriented for mating into the pockets defined onthe trailing, distal side of the shank.

FIG. 13 is a side view (from the driver's side) of the head of thetowing hitch of FIGS. 1-7.

FIG. 14 is a front view of the head of FIG. 13.

FIG. 15 is a rear view of the head of FIG. 13.

FIG. 16 is a top view of the head of FIG. 13.

FIG. 17 is a bottom view of the head of FIG. 13.

FIG. 18 is a front perspective view of the head of FIG. 13, shownwithout the identifying information or trademark on one of the ears.

FIG. 19 is a rear perspective view of the head of FIG. 13.

FIG. 20 is a horizontal cross-sectional view of the head of FIG. 13,taken along lines 20-20.

FIG. 21 is an exploded rear perspective view of the tongue assembly ofFIGS. 1-8, illustrating the manufacturer assembling of the tongueassembly.

FIG. 22 is an angled downward front view of the tongue assembly of FIGS.1-8 and 21.

FIG. 23 is a rear perspective view of the tongue assembly of FIGS. 1-8,21 and 22 shown supporting a dual ball member.

FIG. 24 is a rear perspective view of the tongue member of FIGS. 1-8 and21-23, flipped over.

FIG. 25 is a side view (from the driver's side) of the tongue member ofFIG. 24. The opposing side view (from the passenger's side) is a mirrorimage.

FIG. 26 is a front view of the tongue member of FIG. 25.

FIG. 27 is a top view of the tongue member of FIG. 25. The bottom viewis substantially identical.

FIG. 28 is a cross-sectional view of the tongue member of FIG. 25, takenalong lines 28-28.

FIG. 29 is an exploded rear perspective view of an alternative pintleassembly for use with the shank/head assembly of FIGS. 1-9, illustratingthe manufacturer assembling of the pintle assembly.

FIG. 30 is an angled downward front view of the assembled pintleassembly of FIG. 29.

FIG. 31 is an exploded rear perspective view of an alternativeshank/head assembly.

FIG. 32 is a dimensioned side view, showing the relationship between thecenter of the ball and the pivot axis in each of six user-selectableelevational positions, while at rest and not supporting a towing load.

FIG. 33 is an additional dimensioned side view, showing the relationshipbetween the center of the ball and the pivot axis in each of sixuser-selectable elevational positions, while at rest and not supportinga towing load.

FIG. 34 is a dimensioned side view, showing the relationship between thecenter of the ball and the pivot axis in each of six user-selectableelevational positions, while at maximum downward deflection.

FIG. 35 is an additional dimensioned side view, showing the relationshipbetween the center of the ball and the pivot axis in each of sixuser-selectable elevational positions, while at maximum downwarddeflection.

FIG. 36 is a dimensioned side view, showing the relationship between thecenter of the ball and the pivot axis in each of six user-selectableelevational positions, while at maximum upward deflection.

FIG. 37 is an additional dimensioned side view, showing the relationshipbetween the center of the ball and the pivot axis in each of sixuser-selectable elevational positions, while at maximum upwarddeflection.

FIGS. 38-43 illustrate show the assembly process, performed by the user,to attach the tongue assembly to the shank/head, all taken ascross-sectional views along the longitudinal center plane of the hitchstructure, and not showing the proximal portion of the shank/head andnot showing the ball or trailer (hitching structure which issignificantly downstream of the present invention).

FIGS. 44-46 are end, side and cross-sectional views of the preferredbumper used in the tongue assembly of FIGS. 21 and 38-43.

FIGS. 47-58 are perspective, end and side views of four additionaldifferent bumper embodiments for use in the present invention.

FIG. 59 is a front perspective view of an alternative embodiment of avibration minimization ball mount towing hitch of the present invention.

FIG. 60 is an exploded rear perspective view of the towing hitch of FIG.59, illustrating the manufacturer assembling of the towing hitch.

FIG. 61 is an exploded front perspective view of the shank plate, padand head of the towing hitch of FIGS. 59 and 60.

FIG. 62 is a side view of the shank plate of FIGS. 59-61.

FIG. 63 is a front view of the shank plate of FIGS. 59-62.

FIG. 64 is a top view of the shank plate of FIGS. 59-63.

FIG. 65 is a cross-sectional view of the shank plate of FIGS. 59-64,taken along lines 65-65 from FIG. 62.

FIG. 66 is a side view of the head of FIGS. 59-61.

FIG. 67 is a horizontal cross-sectional view of the towing hitch of FIG.59.

FIG. 68 is a side view of another alternative embodiment of a vibrationminimization ball mount towing hitch of the present invention in a restposition.

FIG. 69 is a side view of the towing hitch of FIG. 68 at a position ofmaximum downward deflection.

FIG. 70 is a side view of the towing hitch of FIGS. 68 and 69, relativeto three additional embodiments, each embodiment having a different dropelevation.

FIG. 71 is a vertical cross-sectional view of yet another alternativeembodiment of a vibration minimization ball mount towing hitch of thepresent invention.

FIG. 72 is an exploded rear view of the towing hitch of FIG. 71.

FIG. 73 is an exploded rear view of a vibration minimization ball mounttowing hitch of the present invention having a different connection tothe tongue.

FIG. 74 is a rear perspective view of the towing hitch of FIG. 73.

While the above-identified drawing figures set forth preferredembodiments, other embodiments of the present invention are alsocontemplated, some of which are noted in the discussion. In all cases,this disclosure presents the illustrated embodiments of the presentinvention by way of representation and not limitation. Numerous otherminor modifications and embodiments can be devised by those skilled inthe art which fall within the scope and spirit of the principles of thisinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the preferred configurations, one portion includes a shank (which canbe a tube or can be solid) which mates inside a square,longitudinally-extending receiver tube mounted on the towing vehicle.The other portion includes a structure for mounting traditional hitchingequipment, such as a hitch head, which subsequently supports a hitchtongue for a tow ball, for directly supporting a tow ball, or forsupporting a weight distribution hitch including a tow ball. Instead ofa hitch tongue for supporting a ball, other hitching structures as knownin the art such as pintles, hooks and rings can alternatively besupported. The two portions are pivotally mounted to each other using apivot pin such as a horizontally extending bolt, so the tow ball orother hitching point can pivot in an arc about the pivot axis andrelative to the receiver tube.

FIGS. 1-28 thus detail a first preferred embodiment of a hitch 100 inaccordance with the present invention, used to transmit a towing forcebetween a towing vehicle (not shown) and a towed load (not shown). Atits leading end, the hitch 100 includes a shank 102 which the userinserts into a square, longitudinally-extending receiver tube (notshown) mounted on the towing vehicle. In this embodiment, the shank 102defines a 2″×2″ profile, including a hitch pin hole 104 through theshank 102 to match the location of the hitch pin hole in a standard2″×2″ receiver tube. Thus the preferred hitch pin hole 104 is a nominal17 mm throughhole with its axis about 80 mm from the proximal/trailingend of the shank 102. For the shank 102 to maintain its orientationrelative to the receiver tube, the shank 102 extends distally beyond thehitch pin hole 104 a significant distance to match the depth of thestandard receiver tube, such as having the axis of the hitch pin hole104 about 88 mm from the distal/leading end of the shank 102. The shank102 in the preferred embodiment shown in FIGS. 1-12 is cast from astrong metal such as 4140 alloy steel, with two recesses 106 on eachside to lighten the weight of the shank 102 without significantlyreducing its bending strength. If desired, indicia 108 such as the brandname, date or location of manufacture, or other identifying informationcan be included, preferably within the recesses 106 so as to beprotected from contact with the receiver tube. Other alternativeembodiments can have the shank 202 formed of solid metal without suchrecesses, or can have the shank 302 formed of hollow metal tubing 361such as the embodiment of FIGS. 59, 60 and 67.

At its trailing end, the hitch 100 includes a hitch head 110. Thepreferred hitch head 110 includes a series of pin or bolt holes 112. Thehole spacing, hole size and geometry of the hitch head 110 are made tofit standard weight distribution and other mounts such as tow balltongue 118, dual tow ball 121, pintle mount 122, hook, ring, step mount,cargo carrier, bike rack, receiver tube mount, etc. For instance, in thepreferred configuration, eight bolt holes 112 are used to provide sixelevational positions. The user can select/adjust which of theelevations to mount a hitch tongue assembly 114, in accordance with theheight-wise elevation best suited for mating with the elevation of thecoupler (not shown) on any particular trailer or other towed load. Thepreferred hitch tongue assembly 114 is best shown and detailed in FIGS.8 and 21-28, including a ball mount opening 116 in the tongue 118 formounting a tow ball 120 such as the dual tow ball 121 shown in FIG. 23.As one alternative to having a ball mount opening 116, one or two ballscould be welded on to the tongue 118. As another alternative to having aball mount opening 116, the hitch head 110 can be used to mount thepintle mount base assembly 122 shown in FIGS. 29-30. The pintle mountbase assembly 122 includes a flat, generally vertical surface 123 withfour internally threaded bolt holes 124 for mounting of a pintle hitch(not shown) as known in the art.

The head 110 is pivotally mounted relative to the shank 102, for limitedpivoting in either a clockwise direction or a counterclockwise direction(when viewed from the side) about a pivot axis 130 during towing. Forinstance, relative to a neutral position as shown in FIG. 2, the head110 can pivot up to about 7° clockwise or up to about 3°counterclockwise before contact between the head 110 and the shank 102limits further pivoting movement.

In the preferred embodiments best shown in FIGS. 14, 17, 18, 20 and 31,the head 110, 210 includes two ears 131, 231 which extend on opposingsides of a pivot pin hole 132 on the shank 102, 202 and the pivotalconnection is provided by a pivot pin 133 extending through head pivotpin holes 134 through each ear 131, 231 as well as a shank pivot pinhole 132 on the shank 102, 202. An alternative but generally equivalentconnection, exemplified by the embodiments of FIGS. 71-74, could be madeusing two ears 531, 631 with pivot pin holes 134 on the shank 502, 602around a single pivot pin hole or dual pivot pin holes 138 on the head510, 610. In broader terms, any sort of hinged or pivoting connectioncan be used to connect the head 110, 210, 310, 410, 510, 610 and theshank 102, 202, 302, 402, 502, 602. In the first preferred embodiment,the pivot pin 133 is provided by an internally threaded pivot sleeve135, with two mating externally threaded button head pivot bolts 136,each of which can be formed of stainless steel for ease of installationat assembly, corrosion resistance and appearance. Washers 137 can beprovided for each pivot bolt 136. For instance, the sleeve 135 can havea cylindrical outer diameter of about 22 mm, and a wall thickness ofabout 3 mm, internally threaded for 5/8-11 UNC 2B pivot bolts 136.

Preferably the pivot sleeve 135 has a portion 138 with a knurled outersurface aligning for contact against one of the ears 131. The knurledouter surface 138, such as having knurls which are about 0.8 mm greaterin outer diameter, engages with the hole 134 through the ear 131 toprevent the pivot sleeve 135 from rotating relative to the head 110during use of the hitch 100. By having the pivot sleeve 135 fixedrelative to the head 110, the pivot bolts 136 have no tendency to losetorque and back out during use of the hitch 100. Alternative structuressuch as adhesives or keying could be equivalently used so the pivot pin133 remains fixed during use of the hitch 100 relative to whichever part(shank 502, 602 or head 110, 210, 310, 410) provides the abuttingsurface for the bolt head 139, 239, 339, 439, 530. In the most preferredembodiment, in addition to the knurled outer surface 138, the pivotsleeve 135 is secured to the head 110 with an adhesive such as LOCTITE263. LOCTITE 263 is ideal for dissimilar metals (such as stainless steeland zinc plated carbon steel), has a quick cure time, and can be removedwith the application of heat.

In the alternative embodiments of FIGS. 31-37, 59-60 and 71-72, thepivot pin 133 is formed from a single stainless steel bolt 240, 340,540. A nut 241 secures such bolts 240, 340, 440 in place, although thebolt threads 242 could alternatively be received in internal threads(not shown) provided in one of the ears 231, 331, 531. In the embodimentof FIGS. 31-37, the bolt 240 includes a standard hexagonal head 243received in a hexagon recess 244 on the head 210, which prevents thebolt 240 from rotating with respect to the head 210. In the embodimentof FIGS. 59-60, the bolt 340 is a shoulder bolt and a square shoulder345 on the bolt 340 mates into a square opening 346 through one of theears 331.

In the alternative embodiment of FIGS. 73-74, the pivot pin 133 isformed by a bar 647 which has no head, but instead can be received suchas through a press fit into the corresponding ears 631 of the shank 602.The headless pivot bar 647 preferably includes a keyed end 648 having ashape that more strongly prevents the pivot bar 647 from rotatingrelative to the shank 602. If desired, a set screw (not shown) orsimilar structure can be used to secure the pivot bar 647 relative tothe shank 602, such as downwardly directed in one of the ears of theshank 602 into the flat of the keyed end 648.

Given that the pivot sleeve 135, bolt 240, 340, 540 or bar 647 or otherpivot pin 133 remains fixed relative to either the head 110, 210, 310,410, 510, 610 or the shank 102, 202, 302, 402, 502, 602 during use ofthe hitch 100, 200, 300, 400, 500, 600, a pivoting sliding motion occursinternally against one of the hole(s) 132, 134 through the head 110,210, 310, 410, 510, 610 or shank 102, 202, 302, 402, 502, 602. Forinstance, in the first embodiment, the pivot sleeve 135 rubs against theinside surface of the hole 132 through the shank 102. To minimizefriction associated with this pivoting, a grease zerk 149 is providedthrough the shank 102 in communication with the hole 132 for the pivotsleeve 135, as best shown in FIGS. 9 and 12. The grease zerk 149lubricates the pivot point and the sides of the cavity defining surfaceswhich rub against each other whenever there is relative motion betweenthe tow ball 120 and the shank 102.

Use of the detachable structure for the pivot pin 133 allows theresilient insert(s) 150, 250, 350, 550 to be readily changed for anappropriate durometer pad for a given hitch tongue weight of the towedload. Use of the detachable bolt 140, 240, 340, 540 for the pivot pin133 also allows the resilient insert(s) 150, 250, 350, 550 to be readilyreplaced should it or they degrade due to time or excessive wear. Insome embodiments, replacement of the pad(s) 150, 250, 350, 550 can beperformed by the user. In other embodiments, the spacing between theshank portion 102, 202, 302, 402, 502, 602 and the head portion 110,210, 320, 410, 510, 610 (i.e., the thickness dimension of the pocket),is smaller than the thickness of the pad(s) 150, 250, 350, 550, and thepad(s) 150, 250, 350, 550 must be pre-compressed during assembly. Suchpre-compression involves significant compressive forces (hundreds orthousands of pounds) which can be professionally achieved with properpreloading equipment, but exceed the force which can be applied by handto compress the pad(s) 150, 250, 350, 550. Similarly, releasing theknurled relationship, removal of the adhesive material, and/or releasingthe press fit may require professional assistance to change betweendifferent pad(s) 150, 250, 350, 550 in the hitch 100, 200, 300, 400,500, 600.

A resilient insert 150, 250, 350, 550 is positioned between opposingsurfaces on the shank 102, 202, 302, 402, 502, 602 and the head 110,210, 310, 410, 510, 610. While alternative embodiments could be based ontensioning the resilient insert, the preferred embodiments compress atleast a portion of the resilient insert 150, 250, 350 during pivotingmotion of the head 110, 210, 310, 410, 510, 610 relative to the shank102, 202, 302, 402, 502, 602. In the preferred embodiments, theresilient insert 150, 250, 350, 550 is one or more energy-absorbing,elastically deforming pad(s) disposed in a pocket. The shank 102provides a first biasing surface 151 extending above the pivot axis 130and a second biasing surface 152 extending below the pivot axis 130,both for contact with the pad 150. Likewise, the head 110 provides athird biasing surface 153 extending above the pivot axis 130 and afourth biasing surface 154 extending below the pivot axis 130, both forcontact with the pad 50. Pivoting of the head 110 relative to the shank102 in one direction (counterclockwise as shown in FIG. 2, clockwise asshown in FIG. 3) compresses the insert 150 between the first biasingsurface 151 and the third biasing surface 153, while pivoting of thehead 110 relative to the shank 102 in the opposite direction (clockwiseas shown in FIG. 2, counterclockwise as shown in FIG. 3) compresses theinsert 150 between the second biasing surface 152 and the fourth biasingsurface 154. In the first four preferred embodiments, each of thesebiasing surfaces 151, 152, 153, 154 extends generally vertically. Butthe important aspect is that each biasing surface 151, 152, 153, 154extends significantly in a radial direction relative to the pivot axis130 (i.e., not entirely circumferentially around the pivot axis 130), sothe resilient insert(s) 150, 250, 350, 550 can be compressed betweenopposing biasing surfaces when pivoting occurs. The shape of thecavities in the shank 102 and in the head 110 as best shown in FIG. 12were specifically designed to maximize the shape and volume of the pad150 to achieve the desired force versus displacement characteristics,damping effect and wear resistance. The unusual shape of the insert 150wraps around the pivot point 130. By having the insert 150 wrap aroundthe pivot point 130, the hitch 100 can have a small horizontalseparation (in the most preferred embodiment, only 61 mm) between thepivot point 130 and the line of eight pin attachment holes 112.

In the preferred embodiments, one side of the pad 150, 250, 350 (belowthe pivot axis 130) is compressed for the tow ball 120 to pivotdownward, while a different side of the pad 150, 250, 350 (above thepivot axis 130) is compressed for the tow ball 120 to pivot upward.Using a single pad 150 extending around the pivot axis 130 helps to holdthe pad 150 in place during assembly and use. The single insert 150,250, 350 also helps to minimize movement of the insert 150, 250, 350 andavoid unwanted wear and abrasion, improving overall performance.Alternatively, the single resilient insert of the preferred embodimentcould be replaced with two or more resilient inserts 550, as exemplifiedby the embodiments of FIGS. 71-72 and 73-74. In all embodiments, theshape of the pad(s) 150, 250, 350, 550, and particularly the sizes andangles that the biasing surfaces 151, 152, 153, 154 contact the pad(s)150, 250, 350, 550, contribute to the compressive characteristics of thepad(s) 150, 250, 350, 550.

The resilient insert 150, 250, 350, 550 biases against movement of thetow ball 120 relative to the shank 102, 202, 302, 402, 502, 602. In thepreferred embodiments, the resilient insert 150, 250, 350, 550 isdisposed in a pocket which substantially shields the resilient insert150, 250, 350, 550 at least from sunlight. The pocket between the shank102, 202, 302, 402, 502, 602 and the head 110, 210, 310, 410, 510 whichholds the resilient insert(s) 150, 250, 350, 550 is preferably formed sowater or moisture will not accumulate therein. By shielding the insert150, 250, 350, 550 from sunlight and avoiding water/moisture pooling,the life of the hitch 100, 200, 300, 400, 500, 600 is extended withminimal change over time to the pivoting performance of the hitch 100,200, 300, 400, 500, 600.

The resilient insert 150, 250, 350, 550 is formed of a materialsubstantially more compressible than the metals of the shank 102, 202,302, 402, 502, 602 and the head 110, 210, 310, 410, 510, 610. The pad150, 250, 350, 550 can be formed of a natural rubber material, but morepreferably is formed of polyurethane. In selecting the durometer of thepad material, the pad shape, design load (tongue weight), and size andgeometry all need to be factored in for each application. The preferreddurometer is in the range of Shore 75 A to 95 A, with a most preferreddurometer for the depicted embodiments being Shore 80 A±5 durometer witha tensile strength of 7,000-7,200 psi. To the extent possible, the padmaterial should retain a consistent durometer regardless of temperature,as towing using the invention is common with temperatures in NorthAmerica ranging from about −40° F. in northern winters at night to about110° F. or more in desert heat. In testing of the preferred pad 150 andshape of pocket shown in FIGS. 9 and 12, a Shore 80 A polyurethaneinsert 150 provides good force versus displacement characteristics forits wear resistance and durability. In contrast, testing of thispad/pocket shape using a Shore 75 A polyurethane material proved to betoo soft and did not provide adequate resistance, while testing of thispad/pocket shape using a Shore 85 A polyurethane material started to gettoo hard and created issues with material fractures including fractureof the metal. Failure of the metal could be catastrophic and must beavoided.

Further, the shape of the insert 150, 250, 350, 550 is preferably castrather than cut. The casting process allows for more control of theoverall process, removing voids and bubbles particularly on the exposedsurface of the pad 150, 250, 350, 550 and improving the integrity of theinsert 150, 250, 350, 550. Custom casting also allows tighter controlover the polyurethane recipe, vulcanization times, etc. to truly dial inthe most beneficial properties of the insert 150, 250, 350, 550. In thepreferred embodiment, a window 155 is positioned through the shank 102to allow viewing of one particular area on the insert 50. As best shownin FIGS. 9 and 12, the preferred compressible insert 150 includesidentifying information 156 thereon which can be viewed through thewindow 155, such as identifying the date of manufacture of the insert150, the durometer of the insert 150, and/or the tongue weight rating ofthe insert 150. If the insert 150 is formed by casting or molding, theidentifying information 156 can be an embossed part of the casting ormold. Otherwise the identifying information 156 may be printed on theinsert 150 or included in a label adhered to the insert 50.

The shape, size, and durometer of the pad 150, 250, 350, 550 will allaffect the shock absorption. The shape of the insert 150, 250 need notbe the same for the clockwise compression as for the counterclockwisecompression. The pad 150 best shown in FIGS. 9 and 12 has a generallyconstant width between its side faces 157 of 45 mm, but a relativelycomplex thickness profile in the direction of compression. As onealternative, the embodiment of FIG. 31 includes a differently shapedinsert 250 disposed in a rectangular prism pocket. The alternativeinsert 250 includes a top section 258 which has a rectangularcross-section and a bottom section 259 which has a trapezoidalcross-section. The trapezoidal cross-section 259 allows a place for thedeforming material to go during compression or load. As anotheralternative, the insert 350 of FIGS. 60 and 61 includes two side-by-sidetrapezoidal sections 360, allowing bulging when the insert 350 isdeformed during compression. The constant thickness pad shape of otherpreferred embodiments, such as the inserts 550 of FIGS. 71-74, gives thedeforming material less space to “squish” out and relies more strictlyon compression of the material. Different durometers of the insertmaterial will also affect the amount of force it takes to compress andthe smoothness of the compression. This all applies to the length of pad150, 250, 350 above and below the pivot axis 130 as well, i.e., thelengths, widths and angles of the four biasing surfaces 151, 152, 153,154 affect the amount of force it takes to compress and the smoothnessof the compression.

While the preferred pads 150, 250, 350, 550 are solid, alternative padgeometries include one or more hollow cavities (not shown) within thepad. In general, substantially all of the force on the preferred solidpads 150, 250, 350, 550 places the pad 150, 250, 350, 550 in compressionwith little or no shear. The addition of hollow cavities would allowmore energy absorption due to shear deformation of the pad, but suchshear would also contribute to worse wear characteristics for the pad.To the extent possible, the preferred designs attempt to minimizedegradation of the pad 150, 250, 350, 550 such as protecting the pad150, 250, 350, 550 from sunlight and protecting the pad 150, 250, 350,550 from the possibility of contact with a sharp object, so thedurometer of the pad 150, 250, 350, 550 remains consistent over years ofuse.

In preferred embodiments, the pivoting radius of curvature through whichthe tow ball 120 moves (i.e., the distance between the center of theball 120 and the pivot pin axis 130) is within the range 2.5 to 24inches, with weight distribution hitch usage generally having a greaterpivoting radius of curvature. The pivoting radius of curvature throughwhich the tow ball 120 moves determines the moment arm for the forceapplied to the ball 120 by the trailer which compresses the pad 150,250, 350, 550. More preferably the pivoting radius of curvature throughwhich the tow ball 120 moves is within in the range of 3 to 11 inches.For embodiments where the elevation of the tow ball 120 is selectable,the most preferred distance between the center of the tow ball 120 andthe pivot axis 130 is in the range of about 7.5 to 8.5 inches dependingupon the elevation selected by the user as called out in FIG. 33. Forembodiments where the elevation of the tow ball 120 is set such as theembodiments shown in FIGS. 58-61, the four embodiments shown in FIG. 70,the embodiment of FIGS. 71-72 and the embodiment of FIGS. 73-74, themost preferred distance between the center of the tow ball 120 and thepivot axis 130 is in about 4 inches as called out on FIG. 69.

Other than the pad 150, 250, 350, 550, the remaining components can beformed mostly or entirely of steel, but alternatively could be formed ofaluminum, other metals or alloys, or composite materials provided thematerial selected can withstand the stresses imparted during towing. Themetal parts can be cast, machined or formed by welding components. Forinstance, as shown in FIGS. 59, 60 and 67, the shank 302 is formed bywelding a hollow tube 361 to a cast shank plate 362.

In the geometry of the first three preferred embodiments, the pivot pin133 is at the same elevation as the hitch pin hole 104 through the shank102, 202, 302. This tends to align the forces imparted duringacceleration and deceleration of the trailer in the longitudinaldirection of the shank 102, 202, 302 within the receiver tube. In otherpreferred embodiments, such as those shown in FIGS. 68-74, the pivot pinaxis 130 is offset from the centerline of the shank 102, so alongitudinal towing force imparts a moment about the hitch pin makingthe hitch 400, 500, 600 more likely to rattle within the receiver tubeduring use, but also giving the user more options regarding elevation ofthe ball 120. When using any of the embodiments of FIGS. 68-74, the usermay also want to use some additional dampening structure (not shown)associated with the hitch pin to better prevent such rattling.

In all of these embodiments, the ball 120 can only compress the pad 150,250, 350, 550 through circumferential movement of the ball 120 about thepivot pin axis 130. Forces which in the radial direction from the centerof the ball 120 toward or away from the pivot pin axis 130 aretransmitted through the hitch 100 substantially entirely through metalstructures without any compression of the pad 150, 250, 350, 550. In thegeometry of the preferred embodiments shown in FIGS. 1-70, the arcedrange of motion of the center of the ball 120 about the pivot axis 130is substantially vertical, with the radial direction from the center ofthe ball 120 to the pivot axis 130 substantially aligning with thelongitudinal direction. In these configurations, vertical forces,including vertical vibration, is dampened through compression and/orrelaxation of the two (top and bottom) sides 258, 259 of the pad 50,allowing a vertical ball movement of at least ¼ inch. In the preferredembodiments of FIGS. 1-28 and 31-43, changes of up to 4000 pounds ofvertical hitch tongue force (from pressing downward with 2000 pounds offorce to pulling upward with 2000 pounds of force) will causecompression/relaxation of the pad 150, 250 and a substantially verticalmovement of the tow ball 120 relative to the receiver tube of up toabout 1½ inches.

Particularly as called out in the angles for the highest and lowestelevations of the ball 120 on FIGS. 35 and 37 and with the positions inmm called out in FIGS. 32, 34 and 36 and tabulated below, the geometryallows some relative longitudinal movement, up to the maximumpermissible horizontal movement of 16.6 mm as compared to the maximumpermissible vertical movement at all ball 120 elevations of about 32.5mm. TABLES III and V tabulate a comparison between the rest position andthe maximum downward deflection and upward deflection of the ball 120,for each of the six user-selectable elevations. TABLE VI tabulates acomparison between the maximum downward deflection and upward deflectionof the ball 120, for each of the six user-selectable elevations.

TABLE I HITCH AT REST POSITION HORIZONTAL VERTICAL 1 314.1 78.5 2 315.246.8 3 316.3 15.1 4 317.4 −16.7 5 318.5 −48.4 6 319.6 −80.1 TOTAL 5.5158.6 ADJUSTMENT (TOTAL 0.2 6.2 INCHES)

TABLE II UPWARD MAX (3°) POSITION HORIZONTAL VERTICAL 1 308.4 88.2 2311.2 56.6 3 313.9 25 4 316.7 −6.7 5 319.5 −38.3 6 322.2 −69.9 TOTAL13.8 158.1 ADJUSTMENT (TOTAL 0.5 6.2 INCHES)

TABLE III UPWARD MAX VS AT REST HORIZONTAL VERTICAL −5.7 9.7 −4 9.8 −2.49.9 −0.7 10 1 10.1 2.6 10.2 TOTAL TRAVEL 16.4 59.7 (TOTAL INCHES) 0.62.4

TABLE IV DOWNWARD MAX (7°) POSITION HORIZONTAL VERTICAL 1 325 55.7 2322.4 24 3 319.7 −7.6 4 317.1 −39.3 5 314.5 −70.9 6 311.9 −102.6 TOTAL13.1 158.3 ADJUSTMENT (TOTAL 0.5 6.2 INCHES)

TABLE V DOWNWARD MAX VS AT REST HORIZONTAL VERTICAL 10.9 −22.8 7.2 −22.83.4 −22.7 −0.3 −22.6 −4 −22.5 −7.7 −22.5 TOTAL TRAVEL 33.5 135.9 (TOTAL1.3 5.4 INCHES)

TABLE VI DOWNWARD VS UPWARD MAX HORIZONTAL VERTICAL 16.6 −32.5 11.2−32.6 5.8 −32.6 0.4 −32.6 −5 −32.6 −10.3 −32.7 TOTAL TRAVEL 49.3 195.6(TOTAL 1.9 7.7 INCHES)

Note that the first two preferred configurations have a different padgeometry below the pivot axis 130 than above the pivot axis 130. Ingeneral, the pad 150, 250, 350 below the pivot axis 130 is compresseddue to downward forces on the tow ball 120, whereas the pad 150, 250,350 above the pivot axis 130 is compressed due to upward forces on thetow ball 120. Compression of the pad 150, 250, 350 above the pivot axis130 particularly occurs in weight distribution hitches. While thecurrent designs use a single pad 150, 250, 350 with different geometryabove the pivot axis 130 than below the pivot axis 130, the inventioncould alternatively use two separate pads, one above the pivot axis 130and one below the pivot axis 130. The two separate pads could havedifferent durometers to further customize resistance in eitherdirection. During use of a single pad 150, 250, 350, the bottom 159, 259and top 158, 258 use undergo significantly more compression than themiddle of the pad, which undergoes almost no compression. If desired,for embodiments with two separate pads 550, the pads 550 can be spacedso the compressive load across each pad 550 is more consistent.

Note also that the preferred configurations allow more downward movementfrom the rest position than upward movement from the rest position, suchas a target downward deflection of about 7° versus a target upwarddeflection of about 3°. This is to account for the fact that mosttrailers place a downward tongue weight on the tow ball 120. Due totongue weight, for most vibrations, the vibration absorption will occurentirely through compression of the bottom side 159, 259 of the pad 150,250, 350 with little or no compression of the top side 158, 159 of thepad 50.

In the embodiments of FIGS. 31-37 and 59-61, the pad 250, 350 interactsin a single cavity between two parallel generally vertical walls. Theresultant motion places some shear on the pad 50 in addition tocompression. In other embodiments, particularly when two pads 550 areused such as the embodiments of FIGS. 71-73, the pad(s) 550 can beloaded to counteract the movement of the tow ball 120 almost entirely incompression.

Provided the metal structure and pivot pin 133 are designed to besufficiently strong, the identical metal structure can be sold with anyof several available different durometer or different material pads, foruse in towing loads. For instance, the metal structures shown may besold as a Class III hitch bar (maximum gross trailer weight of 6000 lbs.with a maximum trailer tongue weight (TW) of 600 lbs.) with a first,relatively compressible pad installed in the pocket, sold as a Class IVhitch bar (maximum gross trailer weight of 10,000 lbs. with a maximumtrailer tongue weight (TW) of 1000 lbs.) with a second, lesscompressible pad installed in the pocket, or sold as a Class V hitch bar(maximum gross trailer weight of 12000 lbs. with a maximum trailertongue weight (TW) of 1200 lbs.) with a third, even stiffer padinstalled in the pocket. A single metal structure can also be sold withseveral different durometer or different material pads as a kit,allowing the user to tow different loads while changing to theappropriate pad for the load being towed at that particular time.

Other than the lower three positions of the first and secondembodiments, the remaining positions/embodiments all have the center ofthe tow ball 120 at an elevation higher than the pivot axis 130. Thesepreferred elevations of the ball 120 relative to the pivot axis 130 tendto put the primary load path more through the shank 102, 202, 302, 402,502, 602 versus cantilevered. Additionally, in the lower two positions,the pad 150, 250 takes more of a preset in the loaded condition andtherefore has a smaller range of travel/articulation during normal use.The elevations of the six ball positions are skewed upward to partiallycompensate from these effects.

If desired for the best force transmission profile, the pad 150, 250,350, 550 can be pre-compressed (i.e., away from and outside the shankand the head) as a manufacturing step prior to assembly of the vibrationminimization towing hitch 100, 200, 300, 400, 500, 600, thereby changingthe elastic set point of the pad material. As an additional or separateoption and as desired for the best force transmission profile, the pad150, 250, 350, 550 can be additionally compressed during assembly of thevibration minimization towing hitch 100, 200, 300, 400, 500, 600, (i.e.,due to the pad 150, 250, 350, 550 having uncompressed dimensions greaterthan the size of the pocket in which the pad 150, 250, 350, 550 isplaced). In the most preferred embodiment, the pad 150 is tuned for thegeometry of the vibration minimization towing hitch portions to providethe desired vertical vibration dampening while minimizing any horizontaldampening.

For the first four embodiments, the geometry of the pivotingrelationship of the ball 120 relative to the positioning of the pocketdetermines the amount of compressive force of the pad 150, 250, 350relative to the hitch tongue weight supported. In the first threeembodiments, the pocket which receives the pad 150, 250, 350 is betweenthe pivot pin 133 and the ball 120. Such arrangements place a highercompressive force on the pad 150, 250, 350 than the force supported bythe hitch tongue 118. The pivot pin could alternatively be between theball and the pad. By placing the pad on the other side of the pivot pin,the pivot pin is positioned closer to the ball, providing a shortermoment arm for pivoting of the ball (and less mechanical advantage forcompressing the pad) as compared to the depicted embodiments.

TABLE VII below shows the measured pivoting relationship of the ball 120versus hitch tongue weight for the second embodiment of FIGS. 31-37,using the hitch tongue 118 in the lowest position, during the initialloading of the pad 250.

TABLE VII FORCE (lb) DEFLECTION (mm) 0 0 1000 −1.13 1500 −2.09 2000−2.98 2500 −3.56 3000 −4.01 3500 −4.35 4000 −4.65 4500 −4.99 5000 −5.520 −1.15

The preferred embodiments require at least 200 pounds of tongue weightfor each degree of rotation about the pivot pin 133, and more preferable800-1200 pounds of tongue weight for each degree of rotation about thepivot pin 133. As can be seen in TABLE VII, loading 5000 pounds oftongue weight onto the pad 250 caused about 1° of plastic deformation ofthe lower side 258 of the pad 250, i.e., when the 5000 pounds of tongueweight was removed, instead of bouncing all the way back to its originalposition, the embodiment of FIGS. 31-37 left the tongue 118 hanging 1°lower than before this initial loading. If desired, the geometry can beadjusted such that the tongue 118 slopes slightly upward prior to itsinitial loading, expecting a tongue weight loading that will causeplastic deformation and bring the tongue 118 closer to a horizontalposition, either during towing while the expected tongue weight is beingapplied or after towing when the pad 250 does not fully bounce back toits initial size.

Because in the geometries depicted in FIGS. 1-70 the pad 150, 250, 350dampens vertical vibrations significantly more than it dampenshorizontal vibrations, and because the vertical vibration dampeningoccurs mostly through compressive stress on and not torsion of the pad150, 250, 350, wear characteristics of the pad 150, 250, 350 are muchbetter than prior art vibration dampening structures. In the geometriesdepicted in FIGS. 1-70, horizontal (particularlylongitudinally-directed) towing forces are transmitted largely by metalstructures with minimal pad compression, providing a more accurate, lessyielding feel to the hitch 100, 200, 300, 400 when accelerating anddecelerating the towing vehicle. However, because the majority of theobjectionable vibration forces sensed (and/or heard) by the towingvehicle driver are in the vertical plane, the vibration minimizationtowing hitch 100, 200, 300, 400 creates a much better ride experience.

For the last two embodiments, the geometry of the pivoting relationshipof the ball 120 relative to the positioning of the pocket determines theamount of compressive force of the pads 550 not relative to the hitchtongue weight supported, but rather relative to the tow force(acceleration or deceleration) being transmitted through the hitch 500,600. During acceleration, the ball 120 tilts rearward. Duringdeceleration, the ball 120 tilts forward. The majority of theobjectionable vibration forces sensed (and/or heard) by the towingvehicle driver are still transmitted vertically from the head 510, 610through the pivot pin 133, 647 to the shank 502, 602. However, thehitches 500, 600 are still an improvement on the prior art, particularlyeliminating vibration and rattling when the driver accelerates ordecelerates in a jerky fashion.

The hitches 100, 200 of the first two embodiments of FIGS. 1-37 also usea second a significantly compressible member, referred to as a bumper170, in order to further minimize rattle in conjunction with a twopin/bolt assembly. In the location used, the bumpers 170 of the presentinvention minimize rattle both in loaded and unloaded situations. FIGS.38-43 show the two pin/bolt assembly process, performed by the user, toattach the tongue assembly 114 to the shank/head assembly, all taken ascross-sectional views along the longitudinal center plane of the hitchstructure, and not showing the proximal portion of the head 110 and notshowing the ball 120 or trailer. As shown in FIG. 38, the user hasdecided to attach the tongue assembly 114 in the second-to-highestposition in elevation. As shown in FIG. 39, when the user positions thetongue assembly 114 onto the head 110, the bumper 170 interferes withthe head 110 and will not permit the respective pin holes 112 from thehead 110 and the pin holes 171, 175 from the tongue assembly 114 to lineup without compression of the bumper 170. To achieve assembly, the userfirst tilts the tongue assembly 114 (preferably upward), until one(preferably the top) of the sets of pin holes 171, 112 are in alignmentas shown in FIG. 40. Preferably this places the tongue assembly 114 socontact is made at two locations, between the metal face of the head 110assembly and both an edge of the bumper 170 and another metal surface172 of the tongue assembly 114.

The pin holes 112, 171 have enough clearance relative to the pin 173 toallow insertion of the pin 173. For instance, in the preferredembodiment using pins 173, 174 with a nominal 19 mm outer diameter, thepin holes 112 in the head 110 and the pin holes 171, 175 in the tongueassembly 114 are designed at 20 mm±0.5 mm. This results in 1 mm ofnominal tolerance, that can vary in any given unit from about 0.5 mm to1.5 mm, in all cases leaving enough clearance that, so long as the holes112, 171 in the head 110 and tongue assembly 114 are close to beingaligned, the user can insert the (upper) pin 173 through the alignedholes as shown in FIG. 41.

One the first pin 173 is fully inserted, the user can then crankdownward on the end of the tongue 118 and shown by arrow 176, rotatingthe tongue assembly 114 relative to the (upper) pin 173 andsignificantly compressing the bumper 170. The compression force of thebumper 170 will cause the (upper) pin hole 171 of the tongue assembly114 to pull slightly past the corresponding pin hole 112 of the head 110(shown by the dashed line in FIG. 41), with the (upper) pin 173 pressedfirmly against one side of the tongue hole 171 and firmly against theother side of the head hole 112, taking up all the clearance between thepin 173 and its pin holes 112, 171. By cranking the tongue 118 downwardslightly past horizontal (shown at 0.8° past horizontal in FIG. 42), theother (bottom) sets of pin holes 175, 112 line up. While maintaining thedownward force on the end of the tongue 118, the user can then insertthe other (bottom) pin 174.

The amount of downward force on the end of the tongue 118 to align thepin holes 175, 112 depends upon the shape, size, amount of rubberdisplaced, lever arm (of the mount 118), location, and durometer of thebumper 170, but should be a force that typical users can readilyprovide, such as a force between 1 and 75 pounds on the end of thetongue 118. In the preferred geometry shown, the bumper 170 has a momentarm relative to either pin hole 171, 175 which is about one half to onefourth of the length of the moment arm for the force on the end of thetongue 118, so the compressive force of the bumper 170 is about two tofour times as great as the force the user must supply on the end of thetongue 118 to align the pin holes 175, 112, i.e., the preferredcompressive force of the bumper 170 is between about 2 and 300 pounds.In the most preferred embodiment shown, the lever arm from the end ofthe tongue 118 to the upper pin hole 171 is about 5⅓ inches, while themoment arm from the center of the bumper 170 up to the upper pin hole171 is about 1¼ inches, i.e., the geometry provides a mechanicaladvantage of just over 4:1 in applying the force resulting in sufficientcompression of the bumper 170 to allow insertion of the other (bottom)pin 174.

Once releasing the downward force on the end of the tongue 118, thecompressive force of the bumper 170 causes the end of the tongue 118 tospring slightly higher to a generally horizontal position shown in FIG.43. At this point, the compressive force of the bumper 170 takes up theclearance of the pins 173, 174 in both sets of holes 112, 171, 175 asshown in FIG. 43.

The amount of steady state force that the bumper 170 provides to take upthe clearance between the pins 173, 174 and their respective holes 112,171, 175 depends upon the material and geometry of the bumper 170 aswell as the geometry between the head 110 and the tongue assembly 114.The bumper 170 should be made of a material significantly softer thanthe metal of the head 110 and the metal of the tongue 118.Alternatively, the bumper could be provided by a metal spring (notshown), or other structure which uses bending to counteract acompression force. In the preferred embodiment, the bumper 170 is formedof a rubber or polyurethane material. Preferably the compressiblematerial of the bumper 170 has a durometer in the range of 30 A to 55D(90-100 A), with the most preferred material being an 80 A durometerpolyurethane. In the most preferred geometry shown in the drawings, theend of the bumper 170 is nominally compressed 3.4 mm while the pins 173,174 are inserted into their respective holes 112, 171, 175. With themost preferred shape and durometer of the bumper 170, a force of about80 pounds is required to compress the bumper 170 about 3.4 mm. With themost preferred tongue geometry shown, this means the user must push downon the end of the tongue 118 with a force of about 20 pounds tosufficiently compress the bumper 170 to insert the second pin 175.

The bumper 170 of the present invention is particularly good atpreventing rattle in an unloaded situation, when there is no weight orlittle weight being placed on the end of the tongue 118. In a towingsituation, whenever the tongue weight downward force is substantiallyequal to the force the user had to place on the end of the tongue 118 toinsert the second bolt, rattle might occur in the lower bolt hole 112and/or 175. Preferably the bumper 170 is designed and selected fortowing with a different tongue weight. For instance, if the user isrequired to press downward on the tongue 118 with a force of 20 poundsto insert the lower pin 175, then that configuration should not be usedwith a trailer having a tongue weight of around 20 pounds. By keepingthe trailer tongue weight significantly different from the requiredassembly force, rattling during towing loaded situations is alsominimized.

In the embodiment shown in FIGS. 21, 22 and 38-43, a nominal clearanceof 4.6 mm exists between the top and bottom metal edges 172, 177 of thetongue assembly 114 and the face of the head 110. This clearance is whatenables either the top or the bottom sets of bolt holes 171, 175 to beused for insertion of the first pin. In alternative embodiments, asmaller clearance can be provided between the bottom metal edge 177 ofthe tongue assembly 114 and the face of the head 110, prompting the userto only attempt assembly by pressing downward (and NOT pulling upward)on the end of the tongue 118. However, with the preferred embodiment,the tongue assembly 114 is entirely symmetrical about a horizontalbisecting plane, and thus the tongue assembly 114 can be equally usedright side up or flipped over upside down (i.e., the tongue assembly 114has no “top side” and no “bottom side” until assembled). This isparticularly beneficial when using a dual tow ball 121 with twodifferent sizes such as shown in FIG. 23.

FIGS. 47-58 detail four other preferred geometries of the bumper 178,179, 180, 181 that can be used with the present invention. There aremany ways in which the bumper 170, 178, 179, 180, 181 can be attached,including using a threaded stud, a press fit attachment, a magneticattachment, an adhesive attachment, or a screw/fastener attachment 182.

FIGS. 29 and 30 show an alternative pintle mount 122 which can be usedwith the preferred bumper 170 by again including a threaded hole 183 forattachment of the bumper 170 using a threaded bolt or screw 182. Thepintle mount 122 provides a flat vertical receiving surface 123 withfour spaced threaded bolt holes 124 for attachment of a pintle orsimilar head (not shown). In this case, the pintle mount 122 does notprovide a tongue, and thus the 4:1 mechanical advantage described abovefor compressing the bumper 170 is significantly lessened. Assuming thesame geometry of bumper 170 is used as described above, to create the 80lb. compression force on the bumper 170 required for insertion of thesecond (lower) pin 174, the user can press down on the pintle mount 122with a force of about 40 lbs. Alternatively, a greater mechanicaladvantage can be obtained by first attaching the pintle head to thepintle mount 122 before inserting the second pin 174 to attach thepintle mount 122 to the shank/head 102/110.

Note that when the bumper 170 is used in conjunction with the insert150, 250 of either of the first two embodiments, during use there aretwo separate compressible rubber pieces that can absorb vibration, i.e.,that the insert 150, 250 can absorb vibration in addition to the bumper170 absorbing vibration. During use, vibration that would with the priorart be transmitted between the towed load and the towing vehicle can beabsorbed by either or both of the rubber insert 150, 250 and the bumper170, particularly in situations where clearance exists between the twoattachment pins 173, 174 and their holes 171, 175.

FIGS. 71-74 show two embodiments which combine features of the earlierembodiments in a simple, retrofit solution for many types of existingball mounts. In these embodiments, the ball 120 is attached for pivotingon a single horizontal pivot axis 130, with the mount for the pivot pin133 being directly attachable relative to an existing tongue structure584. Two compressible, resilient pads 550 can be used, preferably formedof a similar compressible material to the embodiments described above.The compressibility of these pads 550 allows the ball 120 to tilt orshift forward or rearward to absorb vibration between the towed load andtowing vehicle. In the hitch 500 shown in FIGS. 71 and 72, the shank 502includes an internally threaded cylindrical base 585, and an attachmentbolt 586 attaches the shank 502 into the existing ball mount hole 587 ofthe existing tongue 584. In the hitch 600 shown in FIGS. 73 and 74, theshank 602 includes a downwardly projecting, externally threaded stud688, attached into the existing ball mount hole 587 of the existingtongue 584 with a nut 689.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

The invention claimed is:
 1. A towing hitch to transmit a towing forcebetween a towing vehicle and a towed load, the towing hitch comprising:a shank formed of metal for attachment to a receiver on the towingvehicle, the shank defining a pivot axis, the shank providing a firstbiasing surface and a second biasing surface; a head formed of metalseparate from the shank which is attachable to the shank for limitedpivoting in either a clockwise direction or a counterclockwise directionabout the pivot axis during towing, the head providing a third biasingsurface and a fourth biasing surface; one or more compressible inserts,formed of a material substantially more compressible than the metals ofthe shank and the head, disposed between the shank and the head, suchthat pivoting of the head relative to the shank in the clockwisedirection compresses the one or more compressible inserts between thefirst biasing surface and the third biasing surface, and such thatpivoting of the head relative to the shank in the counterclockwisedirection compresses the one or more compressible inserts between thesecond biasing surface and the fourth biasing surface; and a tow ballsupported by the head, wherein a force on the tow ball in the range of1000 to 5000 pounds, oriented to maximize pivoting of the head relativeto the shank, causes a pivoting within the range of 1 to 5 degrees. 2.The towing hitch of claim 1, wherein the head comprises a tongue membermounted on a head member at any of a plurality of positions, with thetow ball mounted on the tongue member of the head.
 3. The towing hitchof claim 1, wherein the first, second, third and fourth biasing surfaceseach extend generally radially relative to the pivot axis.
 4. The towinghitch of claim 1, wherein the pivot axis is horizontal and transverse toa longitudinal direction of towing vehicle travel.
 5. The towing hitchof claim 1, wherein the one or more compressible inserts are formed of apolymer material, wherein the shank and the head collectively define atleast one pocket for holding the one or more compressible inserts, theat least one pocket substantially shielding the one or more compressibleinserts from sunlight.
 6. The towing hitch of claim 1, wherein the headis attached to the shank with a pivot axis pin, the pivot axis pin beingrotationally fixed relative to one of the shank and the head.
 7. Thetowing hitch of claim 1, wherein the one or more compressible insertshave a complex geometric profile to match a profile of a space betweenthe shank and the head, and wherein the one or more compressible insertsare cast or molded of a polymer material.
 8. A towing hitch to transmita towing force between a towing vehicle and a towed load, the towinghitch comprising: a shank formed of metal for attachment to a receiveron the towing vehicle, the shank defining a pivot axis, the shankproviding a first biasing surface and a second biasing surface; a headformed of metal separate from the shank which is attachable to the shankfor limited pivoting in either a clockwise direction or acounterclockwise direction about the pivot axis during towing, the headproviding a third biasing surface and a fourth biasing surface, the headcomprising a tongue member mounted on a head member at any of aplurality of positions, wherein the tongue member is mounted on the headmember using a plurality of bolts extending through bolt openings on thetongue member and bolt openings on the head member, each bolt having aninsertion clearance relative to at least one of its bolt openings; oneor more compressible inserts, formed of a material substantially morecompressible than the metals of the shank and the head, disposed betweenthe shank and the head, such that pivoting of the head relative to theshank in the clockwise direction compresses the one or more compressibleinserts between the first biasing surface and the third biasing surface,and such that pivoting of the head relative to the shank in thecounterclockwise direction compresses the one or more compressibleinserts between the second biasing surface and the fourth biasingsurface; a tow ball supported by the head and mounted on the tonguemember of the head; and a compressible bumper disposed between thetongue member and the head member with a compression force provided bythe compressible bumper taking up the insertion clearance.
 9. A towinghitch to transmit a towing force between a towing vehicle and a towedload, the towing hitch comprising: a shank formed of metal forattachment to a receiver on the towing vehicle, the shank defining apivot axis, the shank providing a first biasing surface and a secondbiasing surface, wherein the first and second biasing surfaces eachextend generally radially relative to the pivot axis; a head formed ofmetal separate from the shank which is attachable to the shank forlimited pivoting in either a clockwise direction or a counterclockwisedirection about the pivot axis during towing, the head providing a thirdbiasing surface and a fourth biasing surface, wherein the third andfourth biasing surfaces each extend generally radially relative to thepivot axis; one or more compressible inserts, formed of a materialsubstantially more compressible than the metals of the shank and thehead, disposed between the shank and the head, such that pivoting of thehead relative to the shank in the clockwise direction compresses the oneor more compressible inserts between the first biasing surface and thethird biasing surface, and such that pivoting of the head relative tothe shank in the counterclockwise direction compresses the one or morecompressible inserts between the second biasing surface and the fourthbiasing surface; and a tow ball supported by the head rearward of thepivot axis; wherein the first and third biasing surfaces are above thepivot axis, and wherein the second and fourth biasing surfaces are belowthe pivot axis, such that pivoting of the head relative to the shank inthe clockwise and counterclockwise directions involves vertical movementof the tow ball in an arc about the pivot axis.
 10. The towing hitch ofclaim 9, wherein respective shapes of the shank and head provide amaximum upward stop where the head abuts the shank at a location abovethe pivot axis and a maximum downward stop where the head abuts theshank at a location below the pivot axis, wherein the maximum downwardstop positions the tow ball further below an unloaded rest position thatthe maximum upward stop positions the tow ball above the unloaded restposition.
 11. The towing hitch of claim 9, wherein a force on the towball in the range of 1000 to 5000 pounds, oriented to maximize pivotingof the head relative to the shank, causes a pivoting within the range of1 to 5 degrees.
 12. The towing hitch of claim 9, wherein the one or morecompressible inserts are formed of a polymer material, wherein the shankand the head collectively define at least one pocket for holding the oneor more compressible inserts, the at least one pocket substantiallyshielding the one or more compressible inserts from sunlight.
 13. Atowing hitch to transmit a towing force between a towing vehicle and atowed load, the towing hitch comprising: a shank formed of metal forattachment to a receiver on the towing vehicle, the shank defining apivot axis, the shank providing a first biasing surface and a secondbiasing surface, wherein the first and second biasing surfaces eachextend generally radially relative to the pivot axis; a head formed ofmetal separate from the shank which is attachable to the shank forlimited pivoting in either a clockwise direction or a counterclockwisedirection about the pivot axis during towing, the head providing a thirdbiasing surface and a fourth biasing surface, wherein the third andfourth biasing surfaces each extend generally radially relative to thepivot axis; one or more compressible inserts, formed of a materialsubstantially more compressible than the metals of the shank and thehead, disposed between the shank and the head, such that pivoting of thehead relative to the shank in the clockwise direction compresses the oneor more compressible inserts between the first biasing surface and thethird biasing surface, and such that pivoting of the head relative tothe shank in the counterclockwise direction compresses the one or morecompressible inserts between the second biasing surface and the fourthbiasing surface; and a tow ball supported by the head above or below thepivot axis; wherein the first and third biasing surfaces are behind thepivot axis, and wherein the second and fourth biasing surfaces are infront of the pivot axis, such that pivoting of the head relative to theshank in the clockwise and counterclockwise directions involveshorizontal movement of the tow ball in an arc about the pivot axis. 14.The towing hitch of claim 13, wherein a force on the tow ball in therange of 1000 to 5000 pounds, oriented to maximize pivoting of the headrelative to the shank, causes a pivoting within the range of 1 to 5degrees.
 15. A towing hitch to transmit a towing force between a towingvehicle and a towed load, the towing hitch comprising: a shank formed ofmetal for attachment to a receiver on the towing vehicle, the shankdefining a pivot axis, the shank providing a first biasing surface and asecond biasing surface; a head formed of metal separate from the shankwhich is attachable to the shank for limited pivoting in either aclockwise direction or a counterclockwise direction about the pivot axisduring towing, the head providing a third biasing surface and a fourthbiasing surface; and one or more compressible inserts, formed of amaterial substantially more compressible than the metals of the shankand the head, disposed between the shank and the head, such thatpivoting of the head relative to the shank in the clockwise directioncompresses the one or more compressible inserts between the firstbiasing surface and the third biasing surface, and such that pivoting ofthe head relative to the shank in the counterclockwise directioncompresses the one or more compressible inserts between the secondbiasing surface and the fourth biasing surface, wherein the one or morecompressible inserts are formed of polyurethane with a Shore hardness inthe range of 75 to 85 Shore A; with each of the first, second, third andfourth biasing surfaces each extending within a range of 20 to 200 mmfrom the pivot axis.
 16. The towing hitch of claim 15, furthercomprising: a tow ball supported by the head.
 17. The towing hitch ofclaim 16, wherein a force on the tow ball in the range of 1000 to 5000pounds, oriented to maximize pivoting of the head relative to the shank,causes a pivoting within the range of 1 to 5 degrees.
 18. The towinghitch of claim 15, wherein the shank and the head collectively define atleast one pocket for holding the one or more compressible inserts, theat least one pocket substantially shielding the one or more compressibleinserts from sunlight.
 19. A towing hitch to transmit a towing forcebetween a towing vehicle and a towed load, the towing hitch comprising:a shank formed of metal for attachment to a receiver on the towingvehicle, the shank defining a pivot axis, the shank providing a firstbiasing surface and a second biasing surface; a head formed of metalseparate from the shank which is attachable to the shank for limitedpivoting in either a clockwise direction or a counterclockwise directionabout the pivot axis during towing, the head providing a third biasingsurface and a fourth biasing surface, wherein the head is attached tothe shank with a pivot axis pin, the pivot axis pin being rotationallyfixed relative to one of the shank and the head; one or morecompressible inserts, formed of a material substantially morecompressible than the metals of the shank and the head, disposed betweenthe shank and the head, such that pivoting of the head relative to theshank in the clockwise direction compresses the one or more compressibleinserts between the first biasing surface and the third biasing surface,and such that pivoting of the head relative to the shank in thecounterclockwise direction compresses the one or more compressibleinserts between the second biasing surface and the fourth biasingsurface; and a grease zerk for the pivot axis pin, to assist in pivotingof the other of the shank and the head relative to the pivot axis pin.20. The towing hitch of claim 19, further comprising: a tow ballsupported by the head.